It’s all quite whimsical, as are the child-like cartoons drawn by the title character (the cartoons, actually done by Martin, are the film’s single strongest element).

Dean (Martin) is bummed out. For one thing, he’s broken up with his fiancé. Worse, his beloved mother recently died and he’s having a hard time coping.

When his father (Kevin Kline) starts making noises about selling the family’s Brooklyn home, Dean freaks out. It’s not just the loss of his childhood abode…it’s irrefutable proof that Mom’s really gone.

He tries to outrun his grief with a business trip to L.A., where some smarmy slackers at an ad agency want to use his cartoons in a cologne campaign aimed at teenage boys. The job falls through, but something good comes of it : He meets Nicky (Gillian Jacobs), a young woman so simpatico and fun that he extends his visit just to be around her.

Filmmaker Mike Berbiglia has taken that message to heart. While other new directors are bent on referencing other movies and duplicating long-established genres (horror, crime, raunchy comedy), Berbiglia makes movies about what he knows.

And he’s getting really good at it.

A standup comic, Berbiglia made his directing debut in 2012 with “Sleepwalk With Me,” a semi-autobiographical comedy based on his own career, relationship issues and especially a life-threatening sleep disorder.

His followup feature, “Don’t Think Twice,” is also set in the world of professional comedy. It feels so awesomely authentic you just know almost everything in it has actually happened to Berbiglia.

Loosely plotted — to leave room for tons of character development — “Don’t Think Twice” observes the six members of The Commune, a struggling improv group in New York City.

These comics work menial jobs so that they can devote the weekend to putting on shows in a falling-down theater before small but generally appreciative audiences. They’re improv purists who rely on the ticket buyers to pitch ideas which they instantaneously turn into comedy gold.

They live for their hour a week in the spotlight. And for vindication on a larger stage. Maybe, just maybe, they can land a gig on “Weekend Live,” the “SNL”-ish network powerhouse capable of turning unknowns into household names.

They’re a motley bunch. Allison (Kate Micucci) is a big-eyed waif. Lindsay (Tami Sagher) is mostly big — with a hefty trust fund that allows her to live in her own nice apartment while everybody else shares a ratty flat.

Bill (Chris Gerhard) is so timid-looking you wonder he has the guts for improv. Samantha and Jack (Gillian Jacobs, Keenan-Michael Key) are an item; she’s a team player, while he’s perfectly willing to grandstand.

In charge (if that’s the right word) is Miles (Berbiglia), who’s been doing improv the longest and whose chances of stardom peaked years earlier. Now he teaches comedy classes and halfheartedly sleeps with his female students.